For many years, attempts have been made to produce a fabric having the strength and other characteristics of woven or knitted fabrics without having to go through the innumerable steps required to produce such fabrics. To produce woven or knitted fabrics, a yarn must first be produced. Yarns are normally produced by opening and carding fibers and producing a web of fibers. The fiber web is condensed into a sliver from which a roving is produced by doubling and drawing the slivers. A number of rovings are further doubled and drawn to produce a yarn. To produce the final fabric, the yarns are woven by a loom into a woven fabric or are knitted on a complicated knitting machine. Often the yarn has to be sized with starch or other materials before it can be processed on the weaving or knitting machines.
During the past twenty to thirty years, various processes have been developed and attempts have been made to produce a fabric directly from a web of fibers eliminating most if not all of the various steps described above. Some of these methods involved the use of pins or needles disposed in a pattern. The needles are inserted through a fiber web to produce openings in the web and simulate the appearance of a woven fabric. The resultant product is weak and requires the addition of a chemical binder to produce desired strength. The addition of binder substantially modifies the hand, flexibility, drape and other desirable physical properties and makes it virtually impossible to duplicate the desired properties of woven or knitted fabrics. Other techniques have involved the use of fluid or liquid forces, which are directed at the fiber web in a predetermined Pattern to manipulate the fibers in a manner that the product produced has some of the characteristics of woven or knitted fabrics. In some of these prior techniques the fiber web is supported on a member having a predetermined topography while being treated with fluid forces to alter the fiber configuration and produce a nonwoven fabric. Examples of methods for producing nonwoven fabrics are disclosed and described in U.S. Pat. Nos. 1,978,620; 2,862,251; 3,033,721; 3,081,515; 3,485,706; and 3,498,874.
While fabrics, produced by some of the methods previously described, have been successful commercially, the resulting fabrics still have not had all of the desired characteristics of many woven and/or knitted fabrics. All of these techniques have lacked the ability to obtain either the desired combinations of physical properties in the final fabric or the desired appearance of a woven or knitted fabric or both. The prior art methods have lacked precise control of fiber placement and control of the forces impinging on the fibrous web.
Generally, a fabric should be of uniform construction and have good strength. The fabric should have good clarity or openness, even if the fabric is of a relatively high weight. The fabric should be low linting yet absorbent. The desired combination of properties should be obtainable without the addition of chemical binders. The process should be controllable so as to allow the production of fabrics having desired combinations of physical properties.